The present invention relates to a process for converting olefins directly to cyclic alkylene carbonate esters in a single step in the presence of a gaseous mixture of carbon monoxide and a molecular oxygen containing gas.
Cyclic carbonate esters resembling cyclic esters of vicinal glycols are well known in the art. They are useful as solvents for polymers and for selective extraction procedures. They are also intermediates for preparing epoxides, glycols, ethanolamines, polyesters and other glycol esters. Because of the ability of cyclic alkylene carbonates to react with the evolution of carbon dioxide, they may also find use as blowing agents for preparing foamed plastic or elastomeric compositions.
The more common methods for preparing cyclic alkylene carbonate esters can be classified broadly according to the starting reactants employed, namely, alkylene oxides, vicinal chlorohydrins, or olefins.
Representative of the alkylene oxide route is U.S. Pat. No. 2,773,881 which reacts an epoxide with carbon dioxide, employs a nitrogen-base catalyst such as an amine, e.g. primary, secondary and preferably tertiary amines (trimethylamine, piperidine), in conjunction with pressures of CO.sub.2 above 500 psi and tempratures of 100.degree. to 400.degree. C.
Other catalysts suitable for use in the alkylene oxide routine as described in the background of U.S. Pat. No. 4,224,223 include quarternary ammonium halides, quarternary ammonium hydroxides, sodium bicarbonate, ion-exchange resins, bis-(aminoethoxy) tin compounds, and polyhalogenated 5- or 6-membered ring hydrocarbons.
Representative of the halohydrin route are U.S. Pat. Nos. 2,784,201; 3,923,842; 4,226,778; and 4,231,937.
More specifically, U.S. Pat. No. 2,784,201 is directed to a process for making ethylene carbonate wherein sodium alkyl carbonate is reacted with ethylene chlorohydrin to form the alkyl hydroxyalkyl carbonate which in turn undergoes an internal ester exchange to form the ethylene carbonate. No catalyst is employed and the reaction is conducted at atmospheric pressure.
U.S. Pat. No. 3,923,842 is directed to a process wherein a vicinal halohydrin is reacted with carbon dioxide, in a solvent and in the presence of an amine catalyst compound, i.e., primary, secondary or tertiary amines, e.g. triethylamine. The vicinal halohydrin can be prepared by reacting an olefin with oxygen in the presence of an iron halide and a copper halide producing ferric oxide as a co-product. At Col. 3, Lines 27 et seq, a three step process for the production of an oxirane compound is disclosed wherein an olefin is converted to a halohydrin; the halohydrin converted to the cyclic carbonate ester with CO.sub.2 and an amine; and the cyclic carbonate ester decomposed to the oxirane compound and CO.sub.2. The production of the halohydrin from an olefin and subsequent conversion to the cyclic carbonate ester in a single reaction mixture is not disclosed.
U.S. Pat. No. 4,226,778 is directed to a process for synthesizing cyclic alkylene carbonate esters wherein a vicinal halohydrin is reacted with a quarternary: ammonium, phosphonium, arsonium or stibonium-bicarbonate, in the presence of CO.sub.2 and an organic diluent. Elevated CO.sub.2 pressures are preferred.
U.S. Pat. No. 4,231,937 is directed to a process for synthesizing cyclic alkylene carbonate esters, wherein an alkylene iodohydrin is reacted with CO.sub.2 in the presence of molecular oxygen and a catalyst mixture comprising (1) an iodide of the metals of Groups IA, IB, IIA, IIb and VIII of the Periodic Table, and (2) a carbonate of the metals of Groups IB, IIA, and IIB of the Periodic table, at a pH of between 3 and 10. Included within the scope of metal iodides are cuprous iodides, and osmium iodides. The iodohydrin can be prepared as described in U.S. Pat. No. 3,923,842 discussed above, i.e. from an olefin. However, the in-situ preparation of the iodohydrin in the presence of CO.sub.2 and oxygen is not disclosed.
Representative of the olefin route are U.S. Pat. Nos. 3,025,305; 4,009,183; 4,224,223; 4,247,465; and 4,325,874.
U.S. Pat. No. 3,025,305 discloses a dual catalyst system to effect formation of the cyclic carbonate ester by the direct oxidation of olefins in the liquid phase with a carbon dioxide and oxygen mixture. The first catalyst component (Catalyst A) is a salt or other compound of a transition metal of atomic numbers 23 to 29, as well as lead and tungsten. Specific metals disclosed are vanadium, chromium, manganese, iron, cobalt, nickel, and copper. Halide salts are the preferred form of Catalyst A. The second catalyst component (Catalyst B) is the halide or hydroxy form of a quarternary ammonium compound.
U.S. Pat. No. 4,009,183 discloses a process for preparing cyclic carbonate esters by reaction, in the liquid phase, between an olefin, carbon dioxide, and oxygen in the presence of a catalyst system consisting of (a) iodine in the form of elementary iodine and the iodides of Groups IA, IIA, IB, IIB, IIIA, IIIB, IVA, VA, VIIB and VIII of the Periodic Table; and (b) an oxygen conveyor selected from manganese dioxide, nitrites, nitrates, nitrogen oxides and a cobalt complex. Preferred iodides include copper iodide. Water, or water solvent mixtures (e.g. 10:1 to 1:10) can be employed. The pH of the reaction mixture is maintained between 3 and 8.
U.S. Pat. No. 4,244,223 is directed to the synthesis of cyclic carbonate esters in the liquid phase by reacting an olefin, and carbon dioxide in the presence of oxygen and using a dual catalyst mixture of (a) iodine or an iodate of a metal of Groups IA, IB, IIA, IIB, VB, VIIB, and VIII of the periodic Table; and (b) an iron compound, copper compound or mixture thereof deposited on an inert support. Osmium is not specifically disclosed as a suitable metal. Cuprous iodide is a suitable iodine containing compound. The supported copper compound includes cuprous or cupric halides. Water or a mixture of water and water miscible solvents can be employed including N,N-dimethylformamide and sulfolane.
U.S. Pat. No. 4,247,465 contains a related disclosure of U.S. Pat. No. 4,224,223, but in the absence of a support.
U.S. Pat. No. 4,325,874 employs a catalyst system similar to U.S. Pat. No. 4,224,223 with the exception that the iron and copper compound of the 2nd catalyst component is replaced with an oxide or weak acid salt of thallium III or gold III.
It will be noted that all of the above discussed patents employ carbon dioxide as a source of the carbonyl group of the cyclic carbonate ester. Furthermore, when the cyclic carbonate ester is prepared from an olefin using CO.sub.2, water is not produced as a co-product.
In contrast, the halohydrin route produces water which can lead to hydrolysis of the carbonate ester, and to problems in separating the resultant glycol from the ester.
It is also known to produce non-cyclic carbonate esters from monohydric alcohols by reacting two of such alcohols with carbon monoxide and oxygen as described in Br. Patent Specification No. 1,303,756. More specifically, the process of this patent employs a catalyst composition which is a complex of a compound of a metal of Groups IB, IIB, or VIII of the Periodic Table. The specific metals illustrated are Cu, Ag, Au, Zn, Cd, Hg, Fe, Co, and Ni. The catalyst complex made from the metals of the above metal compounds, comprises a ligand, which complexes with said metal, selected from organic bases such as pyridine, dipyridyl, phenanthroline, alkyl or aryl phosphines, dimethylsulfoxide, dimethylformamide, quinuclidine, CO, nitriles, malonitrile, succinonitrile, and adiponitrile. The positive charge of the metal/ligand complex is associated with a halide ion. A complex formed from Cu.sub.2 Cl.sub.2 and pyridine is illustrated in Example 1. The deficiencies of this catalyst system are discussed in European patent application (EPA) Pub. No. 71,286, namely, sensitivity to water co-product in the form of reduced selectivity and reaction rate.
The above deficiencies are alleged to be overcome in EPA Pub. No. 71,286 by employing a sulfone in conjunction with a copper compound. The copper may be in the I or II valent state, but preferably a copper II compound is employed. Complexes of copper as identified in Br. Patent Specification No. 1,303,756 containing anions and neutral ligands either preformed or made in-situ can be employed. The preferred catalyst system is a copper I and II halide in conjunction with a tertiary aliphatic amine such as trimethylamine. The alcohol reactant may contain one or more hydroxyl groups. However, it is stated that when the alcohol contains 2 or more of such hydroxyl groups, the resulting carbonate is generally polymeric. Glycols are not specifically illustrated as a suitable alcohol. An inert solvent can be employed in addition to the sulfone. The presence of water in the form of impurities in reaction components (e.g. associated with the sulfolane) is said to be tolerated in the process although it is preferred to remove the water and separate it from the carbonate by azeotropic distillation. The organic amine bases are employed to achieve a molar ratio of base to copper of 0.01 to 1.
By way of further background, it is well known from the technical literature, that olefins can be oxidized to their corresponding diols, stoichiometrically or catalytically with osmium oxide compounds, particularly osmium tetroxide.
The non-catalytic, i.e. stoichiometric, cis-hydroxylation of alkenes with OsO.sub.4 has been conventionally characterized as taking place via the formation, with the alkene, of an osmium (VI) intermediate ester complex. [For a recent review, see, "Osmium Tetroxide Cis Hydroxylation of Unsaturated Substrates", by M. Schroder, Chem. Rev. Vol. 80, pp. 187-213 (1980) hereinafter Schroder].
To convert the non-catalytically prepared osmium (VI) ester complex intermediate to the diol, the intermediate can be hydrolyzed reductively. Reductive hydrolysis is conventionally carried out by using alkali metal sulfites, bisulfites, lithium aluminum hydride, or hydrogen sulfide to yield the corresponding cis-diols together with lower valence forms of osmium which are removed by filtration.
It has been observed by Criegee (See, Schroder, page 191, Col. 1, 11-12) that for non-catalytic cis hydroxylation of alkenes, the rate of formation of the Osmium (VI) ester complex is greatly increased in the presence of tertiary amines such as pyridine. This rate enhancement is believed to occur via the formation of some type of amine Osmium (VI) ester complex (See Schroder page 191, Col. 2). However, enhancement of the rate of the Osmium (VI) ester complex does not necessarily result in an enhancement of the overall hydroxylation rate, since the rate of hydrolysis of the ester complex must also be considered. In this regard, it has been noted that whereas certain osmium ester complexes and amine ester complexes (e.g. with pyridine) can be hydrolyzed reductively, amine ester complexes are more resistant to such hydrolysis. (See Schroder page 191, Col. 2, last paragraph; and page 193, Col. 1, first paragraph).
In contrast to the stoichiometric non-catalytic mode of cis hydroxylation with OsO.sub.4, the catalytic mode employs a secondary oxidant to oxidatively hydrolyzed the intermediate Osmium (VI) ester and regenerate the OSO.sub.4 which can undergo further reduction by the substrate olefin. A variety of oxidants have been employed in conjunction with OsO.sub.4 such as H.sub.2 O.sub.2, t-butylhydroperoxide and oxygen.
The use of oxygen as an oxidant has encountered considerable difficulty due to the appreciable overoxidation of the products, particularly at elevated temperatures (e.g. 70.degree.-80.degree. C.), leading to the formation of keto or acid products. However, if the reaction temperature is lowered to reduce overoxidation, the reaction rate is so low that yields of cis-diol are drastically reduced. An additional disadvantage of the use of oxygen oxidan is that the reaction is highly pH dependent (See Schroder, page 210, Col. 1).
Commonly assigned U.S. Pat. No. 4,390,739 by R. Austin, and R. Michaelson describes a process for the hydroxylation of olefins using oxygen as an oxidant, a catalytically active metal oxide catalyst such as OsO.sub.4, and at least one transition metal salt co-catalyst such as copper bromide. This process can also be conducted in the optional presence of a second co-catalyst such as alkali metal halides. Pyridine is disclosed as a suitable solvent for this process but no mention is made of any promoting effect being associated with this solvent medium. While the use of the transition metal co-catalyst substantially improves the reaction rate and/or selectivity of the hydroxylation reaction, a further improvement in this process is still being sought.
U.S. patent application Ser. No. 310,217, filed Oct. 9, 1981, now abandoned, of common assignee herein by R. Michaelson and R. Austin discloses the use of various osmium halide and oxyhalide catalysts in the presence or absence of a wide variety of co-catalysts and an oxidant selected from hydrogen peroxide, organohydroperoxides, or oxygen. Pyridine is disclosed as a suitable buffer for pH control in this application, which pH control is required when employing hydrogen peroxide.
Commonly assigned U.S. Pat. No. 4,314,088 and a continuation-in-part thereof, namely, U.S. Pat. No. 4,393,253 by R. Austin and R. Michaelson collectively, disclose the use of various halide containing co-catalysts in conjunction with osmium tetroxide catalyst and organohydroperoxide oxidants to hydroxylate olefins. The halide containing co-catalysts include alkali and alkaline earth metal halides, hydrogenhalides, quarternary hydrocarbyl phosphonium halides, halogens, and transition metal halides.
Commonly assigned U.S. Pat. No. 4,413,151, by R. Michaelson, R. Austin, and D. White is directed to a process for hydroxylating olefins in the presence of a supported osmium containing catalyst, optional co-catalyst (e.g. CuBr.sub.2) and an oxidant selected from hydrogen peroxide, organohydroperoxides and oxygen.
Commonly assigned U.S. patent application Ser. No. 420,137 filed Sept. 20, 1982 by R. Michaelson, R. Austin, and D. White, now U.S. Pat. No. 4,486,613, is directed to a process for hydroxylating olefins in the presence of an osmium carbonyl catalyst optional co-catalysts and an oxidant selected from hydrogen peroxide, organohydroperoxide, and oxygen.
While all of the above described commonly assigned patents or patent applications disclose the use of pyridine as one of many suitable solvents, none of these applications show or suggest either alone or collectively, that any promoting effect can be obtained from pyridine when employed for the hydroxylation of olefins, or in accordance with the presently claimed invention.
Moreover, to the best of the inventors' knowledge, not a single prior art publication shows the use of any tertiary amine as a promoter to enhance the overall rate of osmium catalyzed cis-hydroxylation of olefins with oxygen. The catalytic cis hydroxylation of tetra and tri-substituted alkenes with t-butylhydroperoxide and OsO.sub.4 has apparently been conducted. However, the oxidative hydrolysis of such esters has been found to be particularly slow due to steric considerations and particularly in the presence of pyridine (See, Schroder, page 193, Col. 2, first paragraph).
Commonly assigned U.S. patent application Ser. No. 538,190, filed Oct. 3, 1983 by the inventors herein is directed to the use for olefin hydroxylation of heteroaromatic and pseudoheteroaromatic amine promoters, such as pyridine, in a reaction system employing a catalytically active osmium compound, a copper compound (e.g. copper bromide) and oxygen.
Commonly assigned U.S. patent application Ser. No. 604,043, filed Apr. 26, 1984 by the inventors herein is directed to the use of olefin hydroxylation of cycloaliphatic amine based promoters such as DABCO (defined hereinafter) and hexamethylenetetramine in a reaction system similar to that described in connection with the U.S. patent application No. 538,190.
The search has continued for alternative methods for producing cyclic carbonate esters. The present invention is a result of this search.